A typical air blast nozzle used in the past to provide atomized fuel to the combustor of a gas turbine engine is described in the Helmrich U.S. Pat. No. 3,684,186 issued Aug. 15, 1972. Such air blast fuel nozzles utilize compressor discharge air in the form of an inner air flow and from the nozzle with a fuel flow intermediate the air flows to provide atomization and intermixing of fuel and air discharged from the nozzle face downstream thereof. The fuel nozzle disclosed in this patent does not include an igniter for igniting the fuel-air mixture.
The Hopkins U.S. Pat. No. 3,548,592 issued Dec. 22, 1970, discloses a combination fuel nozzle and spark plug for a gas turbine engine. The spark plug is disposed coaxially with the nozzle longitudinal axis within an annular gaseous fuel chamber therearound. Ports are provided to introduce air between the inner electrode of the spark plug and an outwardly spaced grounded electrode merely for cooling the electrodes and purging the space therebetween. The discharge tips of the electrodes protrude downstream of the nozzle face and the spark jumps across the electrode tips transverse to the longitudinal axis in the path of the cooling and purging air exiting from the spark gap.
The Fredriksen U.S. Pat. No. 3,893,296 issued July 8, 1975, illustrates a combustion liner having fuel and air premixing inside the liner upstream of a discharge throat. A central spark igniter extends through the liner and terminates in a discharge tip adjacent the discharge throat. Air is introduced and flowed around and along the igniter merely for cooling it. The spark gap extends between the lower end of the electrode to a surrounding tip of a liner support in the path of the cooling air.
The Morishita U.S. Pat. No. 4,215,979 issued Aug. 5, 1980, describes an ignition torch for a gas turbine engine wherein fuel and air are premixed upstream of the discharge tip of an electrode assembly. An off-axis fuel pipe extends through an annular air chamber that is disposed around the igniter. Fuel from the fuel pipe and air are mixed upstream of an annular wall in the air chamber by turbulence generated by air vents in the wall. The ignition torch is disposed on one side of the combustor of the gas turbine engine while fuel for normal operation is fed into another side of the combustor through a plurality of fuel injection ports in a rotating shaft. The igniter is recessed inside the torch body away from the high temperature combustor environment. 5 The Benedict U.S. Pat. No. 3,057,159 issued Oct. 9, 1962, discloses a rocket igniter having a central electrode along which propellant flows for discharge adjacent the discharge tip. The spark from the igniter is discharged in the path of flowing propellant.
The Izuha et al U.S. Pat. No. 4,412,810 issued Nov. 1, 1983, describes a pulverized coal burner having an off-axis igniter.
Treatice entitled Gas Turbine Combustion authored by Arthur W. Lefebvre and published in 1983 by McGraw-Hill Book Co.--Hemisphere Publishing Corp. at pages 222-230 discusses ignition performance of gas turbine engines. Different types of igniters, such as surface-discharge igniters are discussed. Location of the igniter along the centerline of the combustor liner adjacent to the fuel nozzle is also discussed. However, this location is said likely to cause the igniter face to become fouled by carbon deposits and damaged through over-heating.